(1) Field of the Invention
The present invention relates to a frame type four wheel drive tractor wherein an engine and a transmission mounted on a front and a rear portions of vehicle frames, respectively, are operatively interconnected through a transmission shaft, and the transmission and front wheels are operatively interconnected through a front wheel drive shaft.
(2) Description of the Prior Art
A known example of four wheel drive tractor of this type is disclosed in U.S. Pat. No. 4,574,910 wherein a front wheel drive shaft extends horizontally and a transmission shaft also extends horizontally above the front wheel drive shaft. A step for the operator is disposed above the transmission shaft.
It is necessary to provide a large and flat step for improving operational efficiency of the operator. Furthermore, a low level step is necessary for the operator to board and alight from the vehicle with ease. However, the step should not be lowered at the cost of the level of the vehicle from the ground or, specifically the level of the front wheel drive shaft from the ground. This is because the tractor of this type has often has a working implement such as a mower installed in a lower middle portion thereof and often travel rough terrains, which requires a sufficient clearance to be secured for the front wheel shaft which is positioned in the lowermost portion of the center of the vehicle. However, it is difficult to obtain a fully satisfying result in the foregoing conventional tractor due to limitations caused by the transmission shaft and front wheel drive shaft.
A further example of conventional tractor is disclosed in Japanese Utility Model Laying-open No. 58-132783, which has a gearbox of a front wheel steering mechanism projecting above the step. This structure makes a space for freedom of the driver's feet narrow, as a result of which, the operational efficiency is decreased and positional limitations are given to operation pedals.